This invention relates to improvements in an elevator speed control system.
In elevator systems the elevator car is generally driven through both a mechanical system including an electric motor, a winding mechanism etc. and a rope system and controlled in speed by a speed control system. However, the car does not always travel a distance corresponding to the speed pattern provided by the speed control system due to various external disturbances such as loss occurring in the mechanical system, time delay inherent to the control system, variation in the damping constant of the control system resulting from the change in length of the rope between the winding mechanism and the car which varies in position etc. This has resulted in a disadvantage in conventional speed control systems that the car is difficult to properly accelerate and decelerate attended with a high landing error. On the other hand, the control systems have limitations as to the change in acceleration of the car in view of both a comfortable ride in the car and the traction developed between the winding mechanism and the rope.
Accordingly it is an object of the present invention to provide a new and improved elevator speed control system substantially free from the disadvantages of the prior art practice as described above and decreasing the landing error so that the comfortable ride in the elevator car involved is not deteriorated.